Wood movement calculator
Estimate how much a board will grow or shrink as its moisture content changes with the seasons.
Estimate how much a board will grow or shrink as its moisture content changes with the seasons. Pick your species and grain orientation, and the verified shrinkage figures fill in automatically.
Select a species to see its movement.
How this estimate works
Wood shrinks and swells across its width and thickness as moisture content changes, but barely at all along its length. This calculator uses the nonlinear dimensional-change model from the USDA Forest Products Laboratory Wood Handbook, which accounts for the fact that shrinking and swelling across the same moisture range are close but not perfectly symmetric.
Each species carries its own tangential and radial shrinkage figures, measured green to oven-dry and cross-checked against the Wood Handbook tables. Flatsawn boards use the tangential figure, quartersawn boards use the radial figure. Flatsawn stock moves noticeably more, which is why quartersawn is prized for wide panels and tabletops.
The moisture content presets are typical room-temperature values from the same USDA reference, not a measurement of your actual shop. A moisture meter reading of your specific wood and environment will always be more accurate than a preset.
This is an estimate, not a guarantee. Real boards vary with grain irregularities, finish, and local conditions. Build in extra clearance for movement in any joinery that spans the width of solid wood, such as breadboard ends, frame-and-panel doors, or tabletop attachments.
What is wood movement?
Wood constantly takes on and gives off moisture as the humidity around it changes, and it swells and shrinks as a result, mostly across the grain, barely at all along the length. A tabletop that’s snug in a humid summer can crack in a dry heated winter if it’s built without allowing for this. This calculator estimates how much a given board will move between two moisture levels, so you can leave the right clearance in joinery like breadboard ends, frame-and-panel doors, and tabletop fasteners. The amount depends on the species, how the board was cut (flatsawn moves more than quartersawn), its width, and the size of the moisture swing.
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